The present invention relates to a method for measuring refractive index of a thin film layer formed on medium having a known refractive index.
In the optical engineering field, it is often necessary to measure refractive index of a thin film. It is known to use a polarization analysis method as a noncontact and nondestructive measuring method. However, the ellipsometry method requires a complicated huge apparatus.
In order to conveniently, readily and accurately measure the refractive index of a thin film layer, the applicant of this application proposed a measuring method in Japanese Patent Application Nos. 61-282758 and 61-287495 which disclose a method for measuring refractive index of a thin film layer formed on a substrate having a known refractive index wherein P-polarized monochromatic light and S-polarized monochromatic light are irradiated to the thin film at a predetermined angle of incidence and reflectances Rp and Rs for the P-polarized monochromatic light and the S-polarized monochromatic light are detected and wherein the refractive index of the thin film layer is calculated using the known refractive index of the substrate and the reflectances Rp and Rs in accordance with a predetermined sequence.
However, the proposed method does not consider the absorption effect of the substrate, therefore it can be applied only to a dielectric substrate but cannot be applied to an absorbent substrate unless a compensation process is added.
Also, the proposed method is applied only to a mono-layered film and cannot be applied to a multi-layered film.